Update cmake_minimum_required

Track cmake_mimimum_required defined in SPIRV-Tools dependency.
Remove conditional dependent on older version of CMake.

.github/workflows/continuous_integration.yml

@@ -130,7 +130,7 @@ jobs:
           python-version: '3.7'
       - uses: lukka/get-cmake@acb35cf920333f4dc3fc4f424f1b30d5e7d561b4 # v3.31.4
         with:
-          cmakeVersion: 3.17.2
+          cmakeVersion: 3.22.1
       - name: Setup ccache
         uses: hendrikmuhs/ccache-action@53911442209d5c18de8a31615e0923161e435875 # v1.2.16
         with:

CMakeLists.txt

@@ -30,14 +30,9 @@
 # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
 # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
 # POSSIBILITY OF SUCH DAMAGE.
-cmake_minimum_required(VERSION 3.17.2)
+cmake_minimum_required(VERSION 3.22.1)
 project(glslang)
 
-if (CMAKE_VERSION VERSION_LESS "3.21")
-    # https://cmake.org/cmake/help/latest/variable/PROJECT_IS_TOP_LEVEL.html
-    string(COMPARE EQUAL ${CMAKE_CURRENT_SOURCE_DIR} ${CMAKE_SOURCE_DIR} PROJECT_IS_TOP_LEVEL)
-endif()
-
 set(GLSLANG_TESTS_DEFAULT ON) # Can be turned off, below, based on environment.
 set(GLSLANG_ENABLE_INSTALL_DEFAULT ON) # Can be turned off, below, based on environment.